The present invention relates generally to breathing apparatus and, more particularly, to a pressure driver for a continuous positive airway pressure (CPAP) ventilation system that utilizes pressure measurements in a closed loop control system for maintaining pressure at the patient. The pressure driver may be used in conjunction with a flow generator device to minimize exhalation resistance and reduce the work of breathing.
The use of breathing devices upon respiratory-impaired patients is well known. Generally, such devices assist in patient breathing by allowing the proper exchange of inhaled and exhaled gases while providing positive pressure to the patient's lungs throughout the respiratory cycle in order to prevent lung collapse. Ideally, such devices provide stable CPAP at the patient to facilitate the restoration of functional residual capacity (FRC) and reverse hypoxemia by recruiting collapsed alveoli.
Such breathing devices have proven to be effective in treating patients whose ability to breathe is impaired. For example, babies born with lung disease or premature neonates unable to maintain FRC may benefit from ventilatory support using CPAP therapy. As was earlier mentioned, CPAP therapy delivers a constant stable pressure to the mouth, nose or via a tracheal tube inserted into the infant. Although the use of such breathing devices have generally proven to be suitable for their intended purposes, such devices possess certain design deficiencies which detract from their overall clinical effectiveness in providing respiratory care.
For example, ventilator devices for infants can provide optimal CPAP treatment when delivering a constant and stable pressure to the patient airway. To accomplish this, such ventilator systems typically include a pressure driver for creating a flow of pressurized gas to the patient. The gas is delivered to a patient circuit which comprises the interface between the ventilator and the patient. A valve is typically provided between the gas source and the patient to control the pressure and/or flow of gas delivered to the patient.
Certain prior art infant ventilator devices utilize a manual flow control valve in order to control pressure at the patient. Unfortunately, variations in pressure may occur during CPAP therapy. Such pressure variations may be the result of leakage occurring in the ventilation system. For example, for infant ventilators using a patient interface configured with nostril-engaging stems, leaks may develop over time between the nostril-engaging stems and the infant's nose. If the patient interface is configured as a nasal mask covering the mouth and/or nose, leaks may also occur due to improper fitment of the mask to the patient's face or due to slippage of the mask during ventilation.
Unfortunately, because of the non-adjustable nature of manual flow control valves as used in prior art infant ventilator devices, such leakage in the ventilation system may go undetected and may result in a loss in pressure at the patient. Additionally, many infant ventilator devices of the prior art lack the capability for detecting leakage or detecting disconnections at the patient circuit. Furthermore, infant ventilator devices of the prior art lack the means for correcting for pressure losses at the patient as a result of such leakage and/or disconnections.
As can be seen, there exists a need in the art for a ventilation system that continuously monitors pressure at the patient for feedback to the pressure control mechanism such that accurate and stable positive pressure may be applied at the patient airway. Furthermore, there exists a need in the art for a ventilation system having the capability to detect system leakage and/or patient circuit disconnection such that the ventilation system may compensate for such leakage and thereby deliver the desired pressure to the patient.